[30146] Remember relation columns expand state

https://community.openproject.com/wp/30146

frontend/src/app/components/wp-fast-table/state/wp-table-relation-columns.service.ts

@@ -47,6 +47,7 @@ import {Injectable} from '@angular/core';
 import {QueryResource} from 'core-app/modules/hal/resources/query-resource';
 import {HalResourceService} from 'core-app/modules/hal/services/hal-resource.service';
 import {RelationResource} from 'core-app/modules/hal/resources/relation-resource';
+import {WorkPackageTableHierarchies} from "core-components/wp-fast-table/wp-table-hierarchies";
 
 export type RelationColumnType = 'toType'|'ofType';
 
@@ -65,7 +66,9 @@ export class WorkPackageTableRelationColumnsService extends WorkPackageTableBase
   }
 
   public valueFromQuery(query:QueryResource):WorkPackageTableRelationColumns {
-    return {};
+    // Take over current expanded values
+    // which are not yet saved
+    return this.current;
   }
 
   /**